Radiation-curable coating compositions

ABSTRACT

A radiation-curable coating composition is described which comprises (A) from about 70% to about 99% by weight of at least one polyfunctional acrylate monomer containing at least one internal flexible unit; (B) from about 1% to about 30% by weight of at least one other reactive vinyl or unsaturated monomer provided the reactive vinyl or unsaturated monomer (B) is not the same as the monomer of (A); and (C) from about 0% to about 10% by weight of at least one photoinitiator, provided that the composition is free of methacrylic functionalized colloidal silica. A method of coating a substrate utilizing the radiation-curable compositions of the present invention, and a substrate coated in accordance with the method of the invention are also described.

TECHNICAL FIELD

This invention relates to coating compositions. More particularly, theinvention relates to radiation-curable coating compositions which may bedeposited upon substrates such as polymeric films to improve theirprintability and other surface characteristics.

BACKGROUND OF THE INVENTION

Polymeric films generally are smooth and have low surface tensions dueto their inherent characteristics. Printing on untreated films oftenresults in unsatisfactory print quality due to insufficient surfacewetting and insufficient ink adhesion. There is also the possibility ofsurface contaminants on film surfaces which can further reduce printquality.

Various coatings have been applied to substrates such as polymeric filmsto improve their printability. The improved ink performance of coatedfilms may be due to improved surface tension, altered polarity,different degrees of micro-roughness, or other physical or chemicalfactors. Polymeric coatings can be applied as solutions, emulsions,dispersions, suspensions or 100% solid systems, by a number of methodssuch as roll coating, gravure coating, rod coating, and other methodsknown to those skilled in the art.

Ultraviolet (UV) light or electron, beam (EB) curing of 100% solidsystems is desirable for a number of reasons including high efficiency,high productivity and improved environmental acceptability. With 100%solid systems cured by UV or EB technology, no solvents are required,and this results in reduced pollution possibilities as well as reducedcapital equipment and process costs due to the lack of solventevaporation and recovery requirements. In addition, the absence of asolvent results in higher line speeds without the limitations ofoven-drying capabilities, and curing occurs rapidly at low temperatureswhich reduces process effects on substrates which may be heat-sensitive.The coatings themselves generally have fewer defects and, consequently,improved properties since it is not necessary for solvent molecules todiffuse out of the coating during cure. For the reasons outlined above,space requirements, waste, and energy consumption are also lower withradiation-curable systems.

Radiation curing of polymeric systems may utilize electron beam curingor ultraviolet curing. UV curing of polymeric systems requires thepresence of at least one photoinitiator whereas curing by EB techniquesdoes not require a photoinitiator. With the exception of the presence orabsence of photoinitiator, the formulations cured by either UV or EBtechnology may otherwise be identical.

U.S. Pat. No. 4,008,115 (Fairbanks et al) describes a method of making aseries of laid-on labels each of which has a solvent andabrasion-resistant radiation-cured overcoating. The patentees describeradiation-curable liquids which may be epoxy prepolymers acrylated toprovide terminal polymerizable acrylate groups, or acrylatedpolyether-polyisocyanate prepolymers or oligomers which may be dissolvedin acrylate monomers which are copolymerizable therewith. Suitablemonomers include trimethylolpropane triacrylate,1,4-butanedioldiacrylate, neopentylglycol diacrylate, pentaerythritoltetraacrylate, 1,6-hexane-dioldiacrylate, etc.

U.S. Pat. No. 4,643,730 (Chen et al) also describe radiation-curableformulations for polyethylene film reinforcement relating to disposablediapers. The patentees describe a curable coating composition which is amixture consisting essentially of (a) from about 30% to about 60% byweight of at least one compound selected from the group consisting ofurethane acrylate acrylic oligomers, acrylated acrylic oligomers andepoxy acrylate acrylic oligomers; (b) from 30% to 50% by weight of atleast one compound selected from the group consisting of monofunctionalacrylate monomers, difunctional acrylate monomers and acrylic monomers;and (c) about 0% to 15% by weight of trifunctional acrylate monomerswith the proviso that the component materials total 100% by weight.

U.S. Pat. No. 4,942,060 (Grossa) relates to solid imaging methodsutilizing photohardenable compositions of self-limiting thickness byphase separation. The photohardenable compositions described in thispatent contain at least one photohardenable monomer or oligomer and atleast one photoinitiator. A list of suitable monomers is found in Col.5, line 42 to Col. 6, line 27. Included in the list of suitable monomersare triethylene glycol dimethacrylate, trimethylolpropane triacrylate,ethoxylated pentaerythritoltriacrylate, propoxylated neopentyl glycoldiacrylate and methacrylate, and mixtures thereof.

U.S. Pat. No. 5,418,016 (Cornforth et al) describes radiation-curablecompositions comprising N-vinyl formamide and an oligomer which includesepoxy-acrylate resins, polyester-acrylate resins, polyurethane-acrylateresins, acrylic acrylate resins, vinyl-ether resins, etc. Thecompositions are reported to be useful for a range of applicationsincluding pigmented and unpigmented coatings, printing inks, adhesives,etc.

EP Application 505 737 A1 describes UV curable coating compositionswhich include an acrylated aliphatic urethane in combination with amethacrylic functionalized colloidal silica and acrylic ester monomer.The coating can be applied to a thermoplastic substrate.

U.S. Pat. No. 5,436,073 (Williams et al) describes composite laminatescomprising (A) a substrate sheet of paper; (B) a first coating bonded toone surface of the substrate comprising a radiation-cured acryliccomposition comprising, prior to curing (i) an acrylated ormethacrylated organic polyamino compound, and (ii) an acrylated ormethacrylated organic polyhydroxy compound, and (C) a second coatingcomprising a polyolefin film bonded to the other surface of thesubstrate.

It is generally accepted that the use of multifunctional monomers andcoatings leads to poor adhesion, and the use of monofunctional monomersleads to slow cure speeds and reduced chemical resistance and strengthproperties. For example, U.S. Pat. No. 5,418,016 discloses that highfunctionality monomers give rapid cure speeds and high cross-linkdensity leading to films of high hardness and tensile strength withexcellent chemical resistance. The films, however, suffer from reducedadhesion. Monofunctional monomers, conversely, give slow cure speeds andlow cross-link density resulting in cured films of lower hardness,tensile strength and with reduced chemical resistance.

SUMMARY OF THE INVENTION

A radiation-curable coating composition is described which comprises (A)from about 70% to about 99% by weight of at least one polyfunctionalacrylate monomer containing at least one internal flexible unit; (B)from about 1% to about 30% by weight of at least one other reactivevinyl or unsaturated monomer provided the reactive monomer is not thesame as the monomer of (A); and (C) from about 0% to about 10% by weightof at least one photoinitiator, provided that the composition is free ofmethacrylic functionalized colloidal silica.

In a preferred embodiment, the reactive vinyl monomer (B) is selectedfrom the group consisting of vinyl ethers, mono- or polyfunctionalacrylate monomers or oligomers, and mixtures thereof. A method ofcoating a substrate utilizing the radiation-curable compositions of thepresent invention, and a substrate coated in accordance with the methodof the invention are also described.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention is a radiation-curable coatingcomposition which comprises (A) from about 70% to about 99% by weight ofat least one polyfunctional acrylate monomer containing at least oneinternal flexible unit; (B) from about 1% to about 30% by weight of atleast one other reactive vinyl or unsaturated monomer, provided thevinyl or unsaturated monomer (B) is not the same as the monomer of (A);and (C) from about 0% to about 10% by weight of at least onephotoinitiator, further provided that the composition is free ofmethacrylic functionalized colloidal silica. In another embodiment, thecoating compositions are free of N-vinyl formamide.

The first essential component of the coating compositions of the presentinvention is at least one polyfunctional acrylate monomer containing atleast one internal flexible unit. Throughout this specification andclaims, the terms "acrylic" and "acrylate" are used generally to includederivatives of acrylic acids as well as substituted acrylic acids suchas methacrylic acid, ethacrylic acid, etc., unless clearly indicatedotherwise. The term internal flexible unit is intended to include unitswhere the atoms contained in the unit can generally rotate around thebonds joining the atoms, and such units are within a chain and notterminal. Specific examples of flexible units useful in the presentinvention include ether groups (or hydrocarbyleneoxy groups),particularly aliphatic ether groups, hydrocarbylene groups containing atleast about 8 carbon atoms, etc. Internal ester units are not consideredflexible. The ether groups can be introduced into the polyfunctionalacrylate monomers such as by reacting a polyhydroxy compound with analiphatic oxide such as ethylene oxide or propylene oxide orcombinations of ethylene oxide and propylene oxide to form analkoxylated polyhydroxy compound, and thereafter reacting thealkoxylated polyhydroxy compound with an acrylic acid or acrylic ester.Polyhydroxy compounds containing ether groups also can be obtained bycondensing (or dimerizing, trimerizing, etc.) polyhydroxy compounds suchas ethylene glycol, propylene glycol, etc., to form derivatives such asdiethylene glycol, triethylene glycol, tetraethylene glycol,polyethylene glycol, propylene glycol, dipropylene glycol, tripropyleneglycol, tetrapropylene glycol, polypropylene glycol, etc., andthereafter reacting the ether containing polyhydroxy compound with anacrylic acid or acrylic ester.

The presence of the internal flexible unit in the polyfunctionalacrylate monomers utilized in the coating compositions of the presentinvention results in a coating composition exhibiting improved adhesionto substrates and excellent ink adhesion. The multifunctional nature ofthese monomers results in fast cure and high cross-linking density. Theuse of polyfunctional acrylate monomers containing internal flexibleunits results in a three-dimensional network with flexibility betweencross-links such that adhesion to substrates and subsequent printinginks is enhanced. Although not wishing to be bound by any theory, it isbelieved that the flexibility obtained with the use of thepolyfunctional acrylate monomers containing flexible units reduces thestress at interfaces which would be observed with typical hard,cross-linked coatings, and which would otherwise lead to reducedadhesion.

In one embodiment, the polyfunctional acrylate monomer (A) containing atleast one internal flexible unit may be characterized by the formula

    R--(OC(O)C(X)═CH.sub.2).sub.n                          (I)

wherein R is a hydrocarbyl group containing from about 4 to about 20carbon atoms and one or more flexible units; X is hydrogen or an alkylgroup containing from 1 to 8 carbon atoms; and n is at least 2. Inpreferred embodiments, the flexible units are ether groups, X ishydrogen or methyl and n is 2, 3 or 4. The hydrocarbyl group R may be analiphatic group or an aromatic group, but is preferably an aliphaticgroup. The polyfunctional acrylate monomers containing internal flexibleunits which are useful in the present invention, including thoserepresented by Formula I, may be prepared by procedures well known tothose skilled in the art. One method of preparing such monomers involvescondensing a polyhydroxy compound to form one or more ether oralkyleneoxy linkages or reacting a polyhydroxy compound with an alkalineoxide such as ethylene oxide or propylene oxide to form ether (oralkyleneoxy) linkages and thereafter reacting the intermediate ether andhydroxy-containing compound with sufficient acrylic acid or acrylicester or derivatives thereof to form the desired polyfunctionalacrylate. For example, a useful polyfunctional acrylate monomer can beprepared by condensing or dimerizing ethylene glycol to form diethyleneglycol and thereafter reacting the diethylene glycol with at least twomoles of an acrylic acid or acrylic ester per mole of diethylene glycol.

Specific examples of suitable polyfunctional acrylate monomerscontaining at least one internal flexible unit include the followingcompounds. In the following examples as well as elsewhere in thespecification and claims, unless specifically indicated otherwise, theterm "acrylate" is intended to include substituted as well asunsubstituted acrylates. In particular, the term "acrylate" is intendedto include alkyl acrylates containing from 1 up to 8 carbon atoms andmore particularly the corresponding methacrylate derivatives.

diethylene glycol diacrylate

triethylene glycol diacrylate

tetraethylene glycol diacrylate

polyethylene glycol diacrylate

dipropylene glycol diacrylate

tripropylene glycol diacrylate

tetrapropylene glycol diacrylate

polypropylene glycol diacrylate

glyceryl ethoxylate diacrylate

glyceryl propoxylate diacrylate

glyceryl ethoxylate triacrylate

glyceryl propoxylate triacrylate

trimethylolpropane ethoxylate triacrylate

trimethylolpropane propoxylate triacrylate

neopentylglycol ethoxylate diacrylate

neopentylglycol propoxylate diacrylate

monomethoxy trimethylolpropane ethoxylate diacrylate

pentaerythritol ethoxylate tetraacrylate

pentaerythritol propoxylate tetraacrylate

dipentaerythritol ethoxylate pentaacrylate

dipentaerythritol propoxylate pentaacrylate

di-trimethylolpropane ethoxylate tetraacrylate

Bisphenol A ethoxylate diacrylate

Bisphenol A propoxylate diacrylate

Examples of polyfunctional acrylate monomers containing at least oneinternal flexible unit which is a hydrocarbylene group include1,8-octanediol diacrylate, 1,10-decanediol diacrylate, polybutadienediacrylate, etc.

The coating compositions of the present invention contain from about 70%to about 99% by weight of the polyfunctional acrylate monomerscontaining at least one internal flexible unit. In other embodiments,the radiation-curable coating compositions will contain at least 75% orat least 80% by weight of a polyfunctional acrylate monomer containinginternal flexible units. The molecular weight of the polyfunctionalacrylate monomers (A) may range from about 300 to about 15,000,preferably from about 300 to about 5,000; and more preferably from about300 to about 3,000. The molecular weight may be a calculated molecularweight or an Mn determined by end group analysis.

The radiation-curable coating compositions of the present invention alsocontain at least one other reactive vinyl or unsaturated monomerprovided that the reactive vinyl monomer (B) is not the same as thepolyfunctional acrylate monomer containing at least one internalflexible unit described above. The amount of such other vinyl monomersincluded in the radiation-curable coating composition of the inventionmay range from about 1% to about 30% and is more often from about 1% toabout 20% or 25% by weight. The reactive vinyl or unsaturated monomers(B) useful in this invention include vinyl ethers, mono- andpolyfunctional acrylate monomers or oligomers, vinyl esters, vinylcarboxylic acids, vinyl carboxylic acid salts, vinyl amides, andunsaturated dicarboxylic acids and derivatives thereof such as maleicand fumaric acids and derivatives thereof. In one preferred embodiment,the reactive vinyl monomer (B) is selected from the group consisting ofvinyl ethers and mono- or polyfunctional acrylate oligomers, and theoligomers may or may not contain internal flexible units. In someinstances, oligomers containing flexible units are preferred since theyprovide additional three-dimensional networks with flexibility betweencross-links on curing. In one presently preferred embodiment, thereactive material included in the radiation-curable coating compositionsof the invention is a mono- or polyfunctional acrylate oligomer or amixture of such oligomers and at least one vinyl ether. In anotherpreferred embodiment, the reactive material (B) is at least one vinylether free of any mono- or polyfunctional acrylate oligomers.

Various vinyl ethers can be included in the coating compositions of thepresent invention, and these include ethers containing one or more vinylgroups. The vinyl ethers copolymerize with the acrylates and provide lowviscosity properties to the mixtures and flexibility to the curedcoating compositions. Specific examples of useful vinyl ethers includeethyl vinyl ether, butyl vinyl ether, hydroxy butyl vinyl ether,cyclohexyl vinyl ether, 2-ethylhexyl vinyl ether, octyl vinyl ether,decyl vinyl ether, dodecyl vinyl ether (Rapi-Cure DDVE), octadecyl vinylether, cyclohexane dimethanol monovinyl ether, phenyl vinyl ether,1,6-hexanediol divinyl ether, 1,4-cyclohexane dimethanol divinyl ether(Rapi-Cure CHVE), diethylene glycol divinyl ether, triethylene glycoldivinyl ether (Rapi-Cure DVE-3), tetraethylene glycol divinyl ether,dipropylene glycol divinyl ether, tripropylene glycol divinyl ether,tetrapropylene glycol divinyl ether, and the propenyl ether of propylenecarbonate (Rapi-Cure PEPC). Ethers with more than one vinyl group suchas 1-hexanediol divinyl ether, 1,4cyclohexane dimethanol divinyl ether,diethylene glycol divinyl ether, triethylene glycol divinyl ether,tetraethylene glycol divinyl ether, dipropylene glycol divinyl ether,tripropylene glycol divinyl ether and tetrapropylene glycol divinylether are preferred. Diethylene glycol divinyl ether, triethylene glycoldivinyl ether, dipropylene glycol divinyl ether and tripropylene glycoldivinyl ether are most preferred. The Rapi-Cure vinyl ethers areavailable commercially from International Specialty Products, Wayne,N.J.

Examples of suitable polyfunctional acrylate oligomers useful in theradiation-curable compositions of the invention include the followingtypes of acrylates:

aliphatic polyether urethane acrylates, diacrylates and polyacrylates;

aliphatic polyester urethane acrylates, diacrylates and polyacrylates;

aromatic polyether urethane acrylates, diacrylates and polyacrylates;

aromatic polyester urethane acrylates, diacrylates and polyacrylates;

polyester acrylates, diacrylates and polyacrylates;

polyether acrylates, diacrylates and polyacrylates;

epoxy acrylates, diacrylates and polyacrylates;

polyamine acrylates, diacrylates and polyacrylates; and

acrylated acrylic oligomers.

Acrylates are generally preferred over methacrylates because of highercure speed.

Preferred acrylated oligomers are those containing internal flexibleunits such as aliphatic polyether urethane acrylates, diacrylates andpolyacrylates; aliphatic polyester urethane acrylates, diacrylates andpolyacrylates; aromatic polyether urethane acrylates, diacrylates andpolyacrylates; aromatic polyester urethane acrylates, diacrylates andpolyacrylates; and polyether acrylates, diacrylates and polyacrylates.Most preferred oligomers are aliphatic polyether urethane acrylates,diacrylates and polyacrylates; aliphatic polyester urethane acrylates,diacrylates and polyacrylates; and aliphatic polyether acrylates,diacrylates and polyacrylates.

Polyfunctional acrylate oligomers are available commercially from avariety of sources. Urethane acrylate oligomers are available fromMorton Thiokol under the designations Uvithane 782 and Uvithane 783, andfrom Polymer Systems Corp., Orlando, Fla. under the designationPURELAST. Ebecryl 270 is an acrylated aliphatic urethane oligomeravailable from UCB Radcure, Atlanta, Ga. Epoxy acrylate oligomers areavailable, for example, from UCB Radcure, Atlanta, Ga. under thedesignations Novacure® 3600 and from Shell Chemical Company under thedesignation Epocryl 25A60. Although Epocryl 25A60 contains some volatilesolvent, the product can be mixed with an acrylate monomer such as, forexample, 1,6-hexanediol diacrylate, and the solvent originally presentcan be removed. An example of a commercially available acrylic acrylateoligomer is Novacure 6700 from UCB Radcure. An example of a commerciallyavailable polyamine acrylate oligomer is Novacure 7100 from UCB Radcure.This acrylate functional oligomeric amine is a liquid having a viscosityin the range of 500 to 1500 CPS at 25° C. and a theoretical molecularweight of 800, and the oligomer contains less than 10% of hexanedioldiacrylate.

As noted above, the reactive material utilized in the coatingcompositions of the present invention also may be at least one mono- orpolyfunctional acrylate monomer provided that the polyfunctionalacrylate monomer is different from the polyfunctional acrylate monomer(A) containing at least one internal flexible unit. However, thereactive material (B) also may contain at least one internal flexibleunit. Specific examples of mono- and polyfunctional acrylate monomerswhich can be utilized as a reactive material in the coating compositionsof the present invention include one or more of the following:ethylhexyl acrylate; 2-ethoxyethyl acrylate; cyclohexyl acrylate; laurylacrylate; stearyl acrylate; alkoxylated phenol acrylates; alkoxylatednonylphenol acrylates; nonylphenol acrylate; isobornyl acrylate;acrylated epoxy soya oil; acrylated epoxy linseed oil; caprolactoneacrylate; 2-phenoxyethyl acrylate; benzyl acrylate; monomethoxytripropylene glycol monoacrylate; monomethoxy neopentyl glycolpropoxylate monoacrylate; 1,3-butanediol diacrylate; 1,4butanedioldiacrylate; 1,6-hexanedioldiacrylate; trimethylolpropane triacrylate;glyceryl triacrylate; pentaerythritol triacrylate;pentaerythritoltetraacrylate; dipentaerythritol pentaacrylate;di-trimethylolpropane tetraacrylate; tris(2-hydroxyethyl)isocyanuratetriacrylate, tetrahydrofurfuryl acrylate; isooctyl acrylate; isodecylacrylate; 2-(2-ethoxyethoxy) ethyl acrylate; ethylene glycol diacrylate;propylene glycol diacrylate; neopentyl glycol diacrylate; cyclopentenyloxyethyl acrylate; 9-anthracenyl methyl acrylate; 1-pyrenylmethylacrylate; Fluorescein diacrylate; and 3,8-diacryloyl ethidium bromide.

Acrylate monomers are generally preferred over methacrylate monomersbecause of higher cure speed. Difunctional and polyfunctional acrylatemonomers are preferred for higher cure speed. Generally, the acrylatemonomers with higher molecular weights are preferred due to lowervolatility and lower odor. As the molecular weight is increased,however, there is generally an increase in viscosity so that the upperlimit of molecular weight for monomers and oligomers may be determinedbased on viscosity considerations. A low overall viscosity generally isdesired for fast wetout and coating at high speeds. The monomers andoligomers useful as reactive materials (B) in the present invention havecalculated molecular weights from about 150 to about 15,000, preferablyabout 300 to about 5,000 or 10,000, and more preferably from about 300to about 3,000. The molecular weight is either a calculated molecularweight based on the sum of the atomic weights of the atoms making up themonomer or oligomer, or the molecular weight is a number averagemolecular weight (Mn) which may be determined by end group analysis.

Examples of vinyl esters include vinyl propionate, vinyl acetate, vinyl2-ethyl hexanoate, etc.

In one preferred embodiment, the coating composition of the presentinvention comprises:

(A) from about 70% to about 99% by weight of a first mixture comprising(1) at least one diacrylate monomer obtained by reacting two moles ofacrylic acid or methacrylic acid with one mole of an ethoxylated orpropoxylated aliphatic diol, and (2) at least one triacrylate obtainedby reacting three moles of acrylic acid or methacrylic acid with onemole of an ethoxylated or propoxylated aliphatic triol;

(B) from about 1% to about 30% by weight of at least one mono- orpolyfunctional acrylate oligomer which may optionally contain internalflexible units such as ethoxy and propoxy groups; and

(C) from 0% to about 10% by weight of at least one photoinitiator.

The weight ratio of diacrylate monomer to triacrylate monomer containedin the first mixture may range from about 1 to 9 to about 9 to 1.Preferably the coating composition contains from about 75% or even 80%up to 99% by weight of (A), from about 1 to about 20 or 25% of (B), andfrom 0% to about 5% of (C).

Specific examples of first mixtures comprising at least one diacrylatemonomer and at least one triacrylate monomer include: glycerylpropoxylate diacrylate and glyceryl ethoxylate triacrylate; glycerylethoxylate diacrylate and glyceryl ethoxylate triacrylate; neopentylglycol propoxylate diacrylate and trimethylolpropane propoxylatetriacrylate; etc.

In another preferred embodiment, the above coating composition whichcomprises a first mixture (A) of a diacrylate monomer and a triacrylatemonomer, (B) at least one mono- or polyfunctional acrylate oligomer, and(C) a photoinitiator, may also contain at least one vinyl ether. Any ofthe vinyl ethers described above can be utilized in this combination.The vinyl ethers copolymerize with the acrylates, and their use improvesthe flexibility and low viscosity properties of the compositions of theinvention. The amount of vinyl ether included in such compositions mayrange from about 1% to about 10% by weight.

The coating compositions of the present invention are radiation-curable,and thus, the coating compositions may contain from 0% to about 10%,more often from 0% to about 5% by weight of at least one photoinitiator.A photoinitiator is not required when the coating compositions are to becured by electron beam (EB) processes. A photoinitiator is necessarywhen the compositions are to be cured by ultraviolet (UV) light.Photoinitiators are classified in two major groups based upon a mode ofaction. Cleavage-type photoinitiators include acetophenones, benzoinethers, benzoyl oximes and acyl phosphines. Abstraction-typephotoinitiators include benzophenone, Michler's ketone, thioxanthones,anthraquinone, camphorquinone and ketocoumarin. Abstraction-typephotoinitiators function better in the presence of materials such asamines and other hydrogen donor materials added to provide labilehydrogen atoms for abstraction. In the absence of such added materials,photoinitiation may still occur via hydrogen abstraction from monomers,oligomers or other components of the system.

Examples of photoinitiators which may be used include one or more of thefollowing:

benzophenone

benzyldimethyl ketal

isopropylthioxanthone

bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide

2-hydroxy-2-methyl-1-phenyl-1-propanone

diphenyl(2,4,6-trimethybenzoyl)phosphine oxides

1-hydroxycyclohexyl phenyl ketone

2-benzyl-2-(dimethylamino)-1- 4-(4morpholinyl)phenyl!-1-butanone

α,α-dimethoxy-α-phenylacetophenone

2,2-diethoxyacetophenone

2-methyl-1- 4-(methylthio)phenyl!-2-(4-morpholinyl)- 1-propanone

2-hydroxy-1- 4-(hydroxyethoxy)phenyl!-2-methyl-1-propanone

It is generally preferably to use combinations of photoinitiators toachieve the best possible surface and through cure of coatingcompositions. Reactive photoinitiators, which contain polymerizablegroups, may also be used in order to react the photoinitiator moleculesinto the cross-linked polymer matrix. Photoinitiators are preferablyused in the least amount necessary to get initiation of cure at the linespeed of the process. The cure process is generally more efficient inthe absence of oxygen, for example, in the presence of nitrogen, so agreater amount of photoinitiator is generally required in the presenceof oxygen.

Examples of hydrogen donor materials which may be utilized incombination with photoinitiators include, but are not limited to, one ormore of the following:

ethyl-4-dimethylaminobenzoate

octyl-p-(dimethylamino)benzoate

N-methyldiethanolamine

dimethylethanolamine

triethanolamine

tri-n-propylamine

diethylethanolamine

triethylamine

diisopropylethylamine

diisopropylethanolamine

dimethylaminomethylphenol

tris(dimethylaminomethyl)phenol

benzyldimethylamine

amine acrylates

amine methacrylates

Any appropriate type of lamp, for example, mercury vapor, pulsed xenon,or electrodeless, may be used for UV curing. Choice of photoinitiator orphotoinitiator combinations, with characteristic absorbance spectra,should be matched with the spectral output of the bulb, for example, Hbulb, D bulb, Q bulb, or V bulb, for highest curing efficiency.

In addition to the above-described components, the various compositionsof the present invention may include other additives known to thoseskilled in the art. These additives may include, but are not limited to,pigments, fillers, fluorescent additives, flow and leveling additives,wetting agents, surfactants, antifoaming agents, rheology modifiers,stabilizers, and antioxidants. Preferred additives are those which donot have appreciable absorption in the wavelengths of interest.

Examples of pigments and filler materials include, but are not limitedto, titanium dioxide, hydrophilic silica, hydrophobic amorphous fumedsilica, amorphous precipitated silica, carbon black, and polymerpowders. Examples of flow and leveling additives, wetting agents, andantifoaming agents include silicones, modified silicones, siliconeacrylates, hydrocarbons, fluorine-containing compounds, and non-siliconepolymers and copolymers such as copolyacrylates.

Examples of stabilizers include, but are not limited to:

tetrakis methylene(3,5-di-tert-butyl-4hydroxy-hydrocinnamate)!methane;

thiodiethylene bis(3,5-di-tert-butyl-4hydroxy-hydrocinnamate);

octadecyl 3,5-di-tert-butyl-4hydroxyhydro-cinnamate;

bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate;

methyl (1,2,2,6,6-pentamethyl-4piperidinyl)sebacate; and

decanedioic acid, bis(2,2,6,6-tetramethyl-4-piperldinyl) ester, reactionproducts with 1,1-dimethyl-ethylhydroperoxide and octane.

The radiation-curable coating compositions of the present inventiongenerally are free or substantially free of methacrylic functionalizedcolloidal silica for the type described in EP Patent Application 0 505737 A1. In another embodiment, the coating compositions of the presentinvention are also free or substantially free of N-vinyl formamide.

The radiation-curable coating compositions of the present invention areprepared by mixing the above-described components. The components may bemixed at room temperature with stirring, and mild heating may beemployed in some instances to facilitate mixing. Since the components ofthe composition may undergo some separation during storage, mildagitation or mixing just prior to use is effective to redisperse thecomponents and is recommended.

The following examples illustrate the radiation-curable compositions ofthe present invention. Unless otherwise indicated in the followingexamples, in the specification and in the appended claims, all parts andpercentages are by weight, temperatures are in degrees centigrade andpressures are at or near atmospheric pressure.

In the following examples, the commercial components are identified asfollows:

    ______________________________________                                        Tradename   Chemical          Supplier                                        ______________________________________                                        Novacure ® 3600                                                                       epoxy acrylate oligomer                                                                         UCB-Radcure                                     Ebecryl ® 270                                                                         acrylated aliphatic urethane                                                                    UCB-Radcure                                                 oligomer                                                          Ebecryl ® 8402                                                                        aliphatic urethane diacrylate                                                                   UCB-Radcure                                                 oligomer                                                          Photomer ® 4127                                                                       neopentylglycol propoxylate                                                                     Henkel                                                      diacrylate                                                        Photomer ® 4072                                                                       trimethylolpropane propoxylate                                                                  Henkel                                                      triacrylate                                                       Rapi-Cure ® CHVE                                                                      1,4-cyclohexane dimethanol                                                                      International-                                              divinyl-ether     Specialty Pro-                                                                ducts (ISP)                                     Rapi-Cure ® DDVE                                                                      dodecyl vinyl ether                                                                             ISP                                             Rapi-Cure ® DVE-3                                                                     triethylene glycol divinyl ether                                                                ISP                                             Rapi-Cure ® PEPC                                                                      propenyl ether of propylene car-                                                                ISP                                                         bonate                                                            080 ®   polysiloxane defoamer                                                                           BYK-Chemie                                      361 ®   acrylic copolymer wetting agent                                                                 BYK-Chemie                                      Darocur ® 1173                                                                        2-hydroxy-2-methyl-1-phenyl-1-                                                                  Ciba-Geigy                                                  propanone                                                         Irgacure ® 500                                                                        mixture of benzophenone and                                                                     Ciba-Geigy                                                  1-hydroxy                                                                     cyclohexyl phenyl ketone                                          CGI-1700    mixture of bis(2,6-                                                                             Ciba-Geigy                                                  dimethoxybenzoyl)                                                             (2,4,4-trimethylpentyl)phosphine                                              oxide and 2-hydroxy-2-                                                        methyl-1-phenyl-1-propanone                                       ______________________________________                                    

    ______________________________________                                                             Parts/Wt.                                                ______________________________________                                        Example 1                                                                     neopentyl glycol propoxylate diacrylate                                                              75                                                     Novacure ® 3600    25                                                     Example 2                                                                     trimethylolpropane propoxylate triacrylate                                                           80                                                     Novacure ® 6700    20                                                     Example 3                                                                     dipropylene glycol diacrylate                                                                        30                                                     glyceryl ethoxylate triacrylate                                                                      50                                                     Novacure 3600          20                                                     Example 4                                                                     dipropylene glycol diacrylate                                                                        30                                                     glyceryl ethoxylate triacrylate                                                                      50                                                     Novacure 3600          17.5                                                   CGE-1700               2.5                                                    Example 5                                                                     Photomer 4127          35.1                                                   Photomer 4072          49.3                                                   Ebecryl 270            10.0                                                   BYK-080                0.4                                                    BYK-361                0.2                                                    Darocur 1173           5.0                                                    Example 6                                                                     Photomer 4127          35.0                                                   Photomer 4072          49.4                                                   Ebecryl 270            10.0                                                   BYK-080                0.4                                                    BYK-361                0.2                                                    Rapi-Cure CHVE         5.0                                                    Darocur-1173           5.0                                                    Example 7                                                                     Photomer 4127          35.0                                                   Photomer 4072          49.4                                                   Ebecryl 270            10.0                                                   BYK-080                0.4                                                    BYK-361                0.2                                                    Rapi-Cure DDVE         5.0                                                    Darocur-1173           5.0                                                    Example 8                                                                     Photomer 4127          35.0                                                   Photomer 4072          49.4                                                   Ebecryl 270            10.0                                                   BYK-080                0.4                                                    BYK-361                0.2                                                    Rapi-Cure DVE-3        5.0                                                    Darocur-1173           5.0                                                    Example 9                                                                     Photomer 4127          35.0                                                   Photomer 4072          49.4                                                   Ebecryl 270            10.0                                                   BYK-080                0.4                                                    BYK-361                0.2                                                    CGI-1700               5.0                                                    Example 10                                                                    Photomer 4127          15.4                                                   Photomer 4072          64.0                                                   Ebecryl 270            5.0                                                    BYK-080                0.4                                                    BYK-361                0.2                                                    Rapi-Cure DVE-3        10.0                                                   Irgacure 500           3                                                      Example 11                                                                    Photomer 4127          15.4                                                   Photomer 4072          64.0                                                   Ebecryl 270            5.0                                                    BYK-080                0.4                                                    BYK-361                0.2                                                    Rapi-Cure DVE-3        10.0                                                   Irgacure 500           5.0                                                    Example 12                                                                    Photomer 4127          16.2                                                   Photomer 4072          65.2                                                   Ebecryl 270            5.0                                                    BYK-080                0.4                                                    BYK-361                0.2                                                    Rapi-Cure PEPC         10.0                                                   Irgacure 500           3.0                                                    Example 13                                                                    Photomer 4127          16.4                                                   Photomer 4072          66.0                                                   Ebecryl 8402           5.0                                                    BYK-080                0.4                                                    BYK-361                0.2                                                    Rapi-Cure DVE-3        10.0                                                   Irgacure 500           2.0                                                    ______________________________________                                    

The coating compositions of the present invention as described aboveexhibit improved adhesion to substrates such as polymeric films, papersubstrates, metallic or metallized films, pressure-sensitive adhesivefilms, and paper constructions. The coating compositions also may beused as ink binders and overprint varnishes. The radiation-cured coatingcompositions of the present invention generally impart improved inkadhesion, chemical resistance, moisture resistance, temperatureresistance and weathering resistance to the substrates.

The radiation-curable coating compositions of the present invention maybe applied to various substrates as a coating by any conventional meansknown in the coating art such as by roller coating, brushing, spraying,reverse roll coating, dipping, offset gravure, etc. The coatingcompositions of the present invention may be heated or cooled tofacilitate the coating process and to alter the depth or penetration ofthe liquid into the substrate prior to curing.

The amount of radiation-curable composition applied to one surface of asubstrate may be varied depending upon the characteristics of thesubstrate, the characteristics desired to be imparted to the substrate,and the particular formulation of the curable mixture. If an excess ofthe coating composition is applied to the substrate, the physicalcharacteristics of the substrate may be affected in an undesirablemanner. Also, for economic reasons, it is normally desired to apply thelowest amount of coating needed to obtain the desired results.Typically, the applied coating weights may, depending on the substrateand intended use, range from about 0.1 to about 25 grams/m². More often,applied coating weights are from about 0.5 to about 1.5 grams/m². Atthese levels, the coated substrate is characterized as having increaseddimensional stability, increased strength, increased thermal stability,increased resistance to solvents and moisture and improved printability.The substrates which have been coated with the radiation-curable coatingcompositions can be cured by exposure to known forms of ionizing oractinic non-ionizing radiation. Useful types of radiation includevisible light, ultraviolet light, electron beam, x-ray, gamma-ray,beta-ray, etc. As noted above, if visible light or ultraviolet light isto be used as the form of radiation, a photoinitiator such as thosedescribed above is included in the curable coating composition.Photoinitiators are not required for electron beam curing. One of theadvantages of using radiation to effect curing of the composition isthat polymerization takes place rapidly at ambient temperature, andheating is not necessary. The equipment for generating these forms ofradiation are well known to those skilled in the art. Electron beamradiation and ultraviolet light are the presently preferred forms ofradiation to be used with the compositions of the present invention.

Curing of the coating composition can be effected in a continuous mannerby passing the coated substrate through radiation equipment which isdesigned to provide the coated substrate with sufficient residence timeto completely cure the coating. Curing may be effected at or nearatmospheric pressure or in an inert atmosphere such as nitrogen orargon. An inert atmosphere is preferred. The length of exposurenecessary to cure the coating compositions varies with such factors asthe particular formulation used, the type and wavelength of radiation,dosage rate, the atmosphere, energy flux, concentration ofphotoinitiator (when required), and the thickness of the coating. Forelectron beam curing, dosage rates of from 0.1 to about 10 megarads,generally below 4 megarads, provide the desirable curing. For UV curing,dosage rates of generally 100-500 milli Joules provide the desiredcuring. Generally, the exposure is quite brief and curing is completedin less than about 0.001 to about 0.1 seconds. The actual exposure timerequired to give proper curing for various coatings can be readilydetermined by one skilled in the art with a minimum of experimentation.Excess curing of the coatings generally should be avoided.

Composite laminates can be prepared in accordance with the presentinvention, and said composite laminates comprise

(A) a substrate;

(B) a printable coating bonded to one surface of said substrate, saidcoating comprising a radiation-cured composition of the presentinvention as described above; and

(C) an adhesive on the other surface of said substrate.

The substrate which is included in the composite laminates of thepresent invention may be any of the substrate materials described abovesuch as paper, polymeric films in the form of sheets and strips, etc. Inone preferred embodiment, the substrate is a polymeric film, and a morepreferred embodiment, the substrate is a polymeric film formed from athermoplastic material such as a polyolefin, a polycarbonate, apolyester, etc.

The composite laminates can be prepared by coating one surface of thesubstrate with a radiation-curable coating composition of the presentinvention by the procedures and in the amounts described above. Afterapplication of the curable coating composition to the substrate, thecurable coating is cured by radiation.

Following the application of the radiation-curable coating compositionto one surface of the substrate, an adhesive coating is applied to theother surface of the substrate. The adhesive may be applied to the othersurface either before or after the curable coating on the other surfacehas been radiation-cured. Preferably, the curable coating is curedbefore the adhesive is applied to the other surface of the substrate.

The amount of adhesive applied to the other surface of the substrate mayrange from about 1 to about 100 grams/m², and more often, the amount isin the range of from about 15 to about 45 grams/m². Although anysuitable adhesive may be used including hot melt and pressure-sensitiveadhesives, in one preferred embodiment, the adhesive is apressure-sensitive adhesive. Any adhesive may be applied to thesubstrate which forms an aggressive adhesive bond to the substrate andto any other surface to which the substrate is to be adhered.

Any pressure-sensitive adhesive known in the art can be used inpreparing the composites of the present invention, andpressure-sensitive adhesive compositions are described in, for example,"Adhesion and Bonding," Encyclopedia of Polymer Science and Engineering,Vol. 1, pp. 476-546, lnterscience Publishers, 2d Edition, 1985, thedisclosure of which is hereby incorporated by reference. Suchcompositions generally contain an adhesive polymer such as natural,reclaimed or styrene butadiene rubber, tackified natural and syntheticrubbers, styrene-butadiene or styrene-isoprene block copolymers, randomcopolymers of ethylene and vinyl acetate, ethylene-vinyl-acrylicterpolymers, polyisobutylene, poly(vinyl ether), poly(acrylic)ester,etc., as a major constituent. Other materials may be included in thepressure-sensitive adhesive composition such as resin tackifiersincluding, for example, rosin esters, oil-soluble phenolics orpolyterpenes; antioxidants; plasticizers such as mineral oil or liquidpolyisobutylenes; and fillers such as zinc oxide or hydrated alumina.The selection of the pressure-sensitive adhesive to be used in anycomposites of the invention is not critical to this invention, and thoseskilled in the art are familiar with the many suitablepressure-sensitive adhesives for particular applications.

The composites of the present invention may be prepared in various formsincluding webs which may be in roll form and which can thereafter be cutor slit into strips or sheets of desired dimensions. The order in whichthe radiation-curable coating and the adhesive coating are applied tothe substrate is not critical. In one embodiment, the radiation-curablecoating composition is applied to one surface of the substrate, and theadhesive is thereafter applied to the other surface of the substratefollowed by curing of the radiation-curable coating composition. Inanother embodiment, the radiation-curable coating composition is appliedto one surface of the substrate and cured. Thereafter, an adhesive isapplied to the other surface of the substrate. The adhesive may beapplied to the substrate soon after the radiation-curable coating hasbeen cured, or the adhesive can be applied at a much later time such asjust prior to use. In another embodiment, the curable coating can be puton after the adhesive.

The following examples illustrate the coated substrates and thecomposites of the present invention.

EXAMPLE A

(A) substrate: polyethylene

(B) radiation-cured coating: Example 10

EXAMPLE B

(A) substrate: biaxially oriented polypropylene film

(B) radiation-cured coating: Example 13

EXAMPLE C

(A) substrate: polyethylene film

(B) radiation-cured coating: Example 13

(C) adhesive: pressure-sensitive adhesive

EXAMPLE D

(A) substrate: biaxially oriented polypropylene film

(B) radiation-cured coating: Example 13

(C) adhesive: pressure-sensitive adhesive

The substrates which are coated with the radiation-cured compositions ofthe present invention and the composite laminates in which a substrateis coated with the radiation-cured compositions of the present inventionare characterized as having an improved ink adhesion, chemicalresistance, moisture resistance, temperature resistance and weatheringresistance. The coating compositions of the invention are particularlywell-suited for providing improved adhesion of inks which aresubsequently cured by ultraviolet light.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

I claim:
 1. A radiation-curable coating composition comprising:(A) fromabout 70% to about 99% by weight of at least one polyfunctional acrylatemonomer containing at least one internal flexible unit; (B) from about1% to about 30% by weight of at least one other reactive vinyl orunsaturated monomer provided the reactive monomer is not the same as themonomer of (A); and (C) from about 0% to about 10% by weight of at leastone photoinitiator, provided that the composition is free of methacrylicfunctionalized colloidal silica.
 2. The coating composition of claim 1comprising from about 75% to about 99% by weight of the polyfunctionalacrylate monomer (A).
 3. The coating composition of claim 1 which isalso free of N-vinylformamide.
 4. The coating composition of claim 1wherein the internal flexible unit of the polyfunctional acrylatemonomer (A) is a hydrocarbylene group containing at least 8 carbon atomsor an aliphatic ether group.
 5. The coating composition of claim 1wherein the polyfunctional acrylate monomer (A) contains at least onealiphatic ether group.
 6. The coating composition of claim 5 wherein theether groups are selected from ethoxy, propoxy or combinations of ethoxyand propoxy groups.
 7. A radiation-curable coating compositioncomprising:(A) from about 70% to about 99% by weight of at least onepolyfunctional acrylate monomer containing at least one internalflexible unit; (B) from about 1% to about 30% by weight of at least onereactive vinyl monomer selected from the group consisting of vinylethers, mono- or polyfunctional acrylate monomers or oligomers, andmixtures thereof, provided the polyfunctional acrylate monomer is notthe same as the monomer of (A); and (C) from about 0% to about 10% byweight of at least one photoinitiator, provided that the composition isfree of methacrylic functionalized colloidal silica.
 8. The coatingcomposition of claim 7 comprising from about 75% to about 99% by weightof the polyfunctional acrylate monomer (A).
 9. The coating compositionof claim 7 which is also free of N-vinylformamide.
 10. The coatingcomposition of claim 7 wherein the internal flexible unit of thepolyfunctional acrylate monomer (A) is a hydrocarbylene group containingat least 8 carbon atoms or an aliphatic ether group.
 11. The coatingcomposition of claim 7 wherein the polyfunctional acrylate monomer (A)contains at least one aliphatic ether group.
 12. The coating compositionof claim 11 wherein the ether groups are selected from ethoxy, propoxyor combinations of ethoxy and propoxy groups.
 13. The coatingcomposition of claim 7 comprising at least two polyfunctional acrylatemonomers containing at least one internal flexible unit.
 14. The coatingcomposition of claim 7 wherein the polyfunctional acrylate monomer (A)is selected from the group consisting of diethylene glycol diacrylate,triethylene glycol diacrylate, tetraethylene glycol diacrylate,polyethylene glycol diacrylate, dipropylene glycol diacrylate,tripropylene glycol diacrylate, tetrapropylene glycol diacrylate,polypropylene glycol diacrylate, trimethylolpropane ethoxylatetriacrylate, trimethylolpropane propoxylate triacrylate, glycerylethoxylate diacrylate, glyceryl propoxylate diacrylate, glycerylethoxylate triacrylate, glyceryl propoxylate triacrylate,neopentylglycol ethoxylate diacrylate, neopentylglycol propoxylatediacrylate, and combinations thereof.
 15. The coating composition ofclaim 7 wherein the reactive material (B) comprises a mono- orpolyfunctional acrylate oligomer selected from the group consisting ofaliphatic polyether urethane acrylates, aliphatic polyester urethaneacrylates, aromatic polyether urethane acrylates, aromatic polyesterurethane acrylates, and polyether acrylates.
 16. The coating compositionof claim 7 wherein the reactive material (B) is an oligomer selectedfrom the group consisting of aliphatic polyether urethane acrylates,aliphatic polyester urethane acrylates and aliphatic polyetheracrylates.
 17. The coating composition of claim 7 wherein the reactivematerial (B) is a mono- or polyfunctional acrylate monomer or oligomercharacterized as having a molecular weight of from about 300 to about15,000.
 18. The coating composition of claim 7 wherein the reactivematerial (B) comprises a vinyl ether.
 19. The coating composition ofclaim 7 wherein the reactive material (B) comprises a mixture of atleast one vinyl ether and at least one mono- or polyfunctional acrylateoligomer.
 20. The coating composition of claim 7 also containing one ormore additives selected from the group consisting of pigments, fillers,fluorescent additives, flow and levelling additives, wetting agents,surfactants, antifoaming agents, rheology modifiers, stabilizers, andantioxidants.
 21. A radiation-curable coating composition comprising:(A)from about 70% to about 99% by weight of at least one polyfunctionalacrylate monomer containing at least one internal ether group; (B) fromabout 1% to about 30% by weight of at least one reactive materialselected from the group consisting of vinyl ethers, mono- orpolyfunctional acrylate monomers or oligomers, and mixtures thereofprovided the polyfunctional acrylate monomer is not the same as themonomer of (A); and (C) from about 0% to about 10% by weight of at leastone photoinitiator, provided that the composition is free of methacrylicfunctionalized colloidal silica.
 22. The coating composition of claim 21comprising from about 75% to about 99% by weight of the polyfunctionalacrylic monomer (A).
 23. The coating composition of claim 21 wherein thepolyfunctional acrylate monomer (A) is characterized by the formula

    R--(OC(O)C(X)═CH.sub.2).sub.n                          (I)

wherein R is a hydrocarbyl group containing from about 4 to about 20carbon atoms and one or more ether linkages; X is hydrogen or an alkylgroup containing from 1 to 8 carbon atoms; and n is at least
 2. 24. Thecoating composition of claim 23 wherein X is hydrogen or a methyl group.25. The coating composition of claim 23 wherein n is 2, 3 or
 4. 26. Thecoating composition of claim 21 wherein the polyfunctional acrylatemonomer (A) is the reaction product of an ethoxylated or propoxylatedpolyhydroxy compound with acrylic or methacrylic acid.
 27. The coatingcomposition of claim 21 wherein the reactive material (B) is at leastone mono- or polyfunctional acrylate oligomer selected from the groupconsisting of aliphatic polyether urethane acrylates, aliphaticpolyester urethane acrylates, and aliphatic polyether acrylates.
 28. Thecoating composition of claim 21 wherein (B) comprises a mixture of atleast one vinyl ether and at least one polyfunctional acrylate oligomer.29. A radiation-curable coating composition comprising:(A) from about70% to about 99% by weight of a first mixture comprising (1) at leastone diacrylate monomer obtained by reacting two moles of acrylic acid ormethacrylic acid with one mole of an ethoxylated or propoxylatedaliphatic diol, and (2) at least one triacrylate obtained by reactingthree moles of acrylic acid or methacrylic acid with one mole of anethoxylated or propoxylated aliphatic triol; (B) from about 1% to about30% by weight of at least one mono- or polyfunctional acrylate monomeror oligomer provided the polyfunctional acrylate monomer is differentfrom the monomers of (A); and (C) from about 0% to about 10% by weightof at least one photoinitiator, provided that the composition is free ofmethacrylic functionalized colloidal silica.
 30. The coating compositionof claim 29 wherein the mono- or polyfunctional acrylate monomer oroligomer (B) is an oligomer selected from the group consisting ofaliphatic polyether urethane acrylates, aliphatic polyester urethaneacrylates and aliphatic polyether acrylates.
 31. The coating compositionof claim 29 wherein (B) comprises a mixture of at least one mono- orpolyfunctional acrylate oligomer and at least one vinyl ether.
 32. Thecoating composition of claim 29 comprising from about 80% to 99% byweight of (A), 1% to 20% by weight of (B), and 0% to 5% by weight of(C).
 33. A method of coating a substrate comprising applying to saidsubstrate, a radiation-curable composition of claim 1, and exposing thecoated substrate to a radiation source to cure the coating composition.34. The method of claim 33 wherein the composition contains aphotoinitiator, and the composition is cured by ultraviolet radiation orvisible light.
 35. The method of claim 33 wherein the composition doesnot contain a photoinitiator, and the composition is cured by electronbeam radiation.
 36. The method of claim 33 wherein the substrate is apolymeric film.
 37. A method of coating a substrate comprising applyingto said substrate, a radiation-curable composition of claim 7, andexposing the coated substrate to a radiation source to cure the coatingcomposition.
 38. The method of claim 37 wherein the composition containsa photoinitiator, and the composition is cured by ultraviolet radiationor visible light.
 39. The method of claim 37 wherein the compositiondoes not contain a photoinitiator, and the composition is cured byelectron beam radiation.
 40. The method of claim 37 wherein thesubstrate is a polymeric film.
 41. A substrate coated in accordance withthe method of claim
 33. 42. A substrate coated in accordance with themethod of claim
 37. 43. A multilayer composite comprising:(A) a polymersubstrate; (B) a printable coating on one surface of said substrate,said coating comprising a radiation-cured composition of claim 1; and(C) an adhesive on the other surface of said substrate.
 44. A multilayercomposite comprising:(A) a polymer substrate; (B) a printable coating onone surface of said substrate, said coating comprising a radiation-curedcomposition of claim 7; and (C) an adhesive on the other surface of saidsubstrate.
 45. The composite of claim 44 wherein the substrate is apolymeric film.
 46. The composite of claim 45 wherein the polymeric filmis formed from a thermoplastic material.
 47. The composite of claim 43wherein the adhesive (C) is a pressure-sensitive adhesive.